It is known in the art to reduce parasitic inductance causing surge noise, which is generated in a switching operation of a power converting apparatus having switching elements. In a conventional power converting apparatus, a high-voltage side electric conductor (to which a high-voltage side switching element is mounted) and a low-voltage side electric conductor (to which a low-voltage side switching element is mounted) are arranged in parallel to each other and a distance between the high-voltage side and the low-voltage side electric conductors is made smaller so as to reduce the parasitic inductance, which may cause the surge noise.
A circuit arrangement is known in the art, for example, as disclosed in Japanese Patent Publication No. 2004-080993 (A), which corresponds to U.S. Pat. No. 7,227,259 B2. According to the circuit arrangement, DC port conductors are placed over their entire length in mutual close proximity and separated from each other only by an insulating layer, in order to achieve low parasitic inductances. In addition, substantial partial sectors of DC port conductors are arranged in close proximity to substrate and/or ribbon connectors.
According to another prior-art power converting apparatus, for example, as disclosed in Japanese Patent Publication No. 2001-286158, flow directions of electric currents are opposite to each other between a positive-side plate conductor and a negative-side plate conductor. The positive-side and the negative-side plate conductors are built up across an insulating sheet. Namely, the positive-side and the negative-side plate conductors are arranged close to but separated from each other by only a thickness of the insulating sheet. As a result, the plate conductors are formed in a low-inductance structure.
In a power converting apparatus having switching devices, it is necessary to make smaller a distance between a high-voltage side electric conductor and a low-voltage side electric conductor, in order to further reduce the parasitic inductance. However, in a case that the high-voltage side and the low-voltage side electric conductors are made from one sheet of a conductive plate, by a punching process using ordinary dies and punches, a distance between the electric conductors is limited to almost a thickness of the conductive plate. In other words, it is difficult to form a smaller distance, which is smaller than criteria of stable machining (for example, the thickness of the conductive plate).
It is possible to separately prepare the high-voltage side and the low-voltage side electric conductors and to arrange such electric conductors so that a distance between them is smaller than the thickness. It is, however, necessary to control such a small distance between the electric conductors over their entire length, which may cause an increase of a manufacturing cost.
It is required to reduce a distance between two electric conductors to a smaller value (which is smaller than a thickness of the electric conductors) not only in the power converting apparatus having switching devices but also in other electronic apparatuses, in which a high-voltage side bus bar (corresponding to the high-voltage side electric conductor) and a low-voltage side bus bar (corresponding to the low-voltage side electric conductor) are arranged in parallel to each other. However, in such an electronic apparatus, there is a problem which is the same to that for the above-explained power converting apparatus.